Scaffolding and elevated work platforms are well known in the construction industry. Scaffolding assemblies having self-elevating work platforms, such as the ones manufactured by Hydro Mobile of L'Assomption, Quebec, are particular useful for moving workers and material to various positions on the building exterior. These scaffolding assemblies include a horizontal work platform suspended between a pair of vertical mast towers, which can be raised and lowered along the mast towers. For ease of explanation, such scaffolding assemblies will be referred to hereinafter simply as a “self-elevating platform scaffolding.”
Typically, the work platform is raised and lowered by a “rack and pinion” lift mechanism. Rack and pinion type lift mechanisms use a drive motor mounted under the work platform to turn a pinion, which mates to a vertical rack mounted to the mast tower. In a construction site environment, dirt and debris quickly foul and damage the gear teeth of rack and pinion components. Consequently, rack and pinion type lift mechanisms require frequent maintenance to function properly. The safety and lifting capacity is also a limitation for rack and pinion type lift mechanisms.
Other self-elevating platform scaffoldings have a lift mechanism that uses a pair of hydraulic rams to “climb” the mast towers. Hydraulic rams are pivotally connected to the platform adjacent the mast towers and have hooks mounted to the ends of the upwardly extending piston rods, which engage cross members on the mast towers. Each ram operates in alternating succession to raise and lower the platform. The alternating operation of the paired rams creates an inherent intermittent stepping action in a “climbing” type lift mechanism, which presents safety concerns. A lift mechanism that provides a smooth continuous raising and lowering of the movable platforms is needed to provide a safer work environment.